Build a real-time Authentication Pipeline
Last updated: May 1, 2026
Quick Overview
Design a real-time authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Robinhood
May 1, 202644
14
4,672 solved
Design a real-time authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Robinhood typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
What the Interviewer Expects
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How would you handle a region-wide outage?
- How would you handle schema migrations with zero downtime?
- How do you ensure data consistency across multiple services?
Practice a Similar Problem on Codemia
Solve a related problem with our interactive workspace, get AI feedback, and view detailed solutions.
Solve on CodemiaSample Answer
Requirements
Functional Requirements:
- User Authentication: Support login, logout, and session management for users.
- Multi-Factor Authentication (MFA): Implement MFA for added security during logi...
Capacity Estimation
Capacity Estimation:
To estimate capacity, we'll consider the following:
- Daily Active Users (DAU): Assume Robinhood has 20 million DAUs.
- Peak Usage: During peak trading hours, assume...
Submit Your Answer
